HSS versus tungsten-vanadium drill bits

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moribundman

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What's the best drill bit material for

- drills ranging from 0.5 mm to 2 mm
- drill speed adjustable between 3k and 15k rpm
- drilling up to 2 mm steel, brass, copper and aluminum and up to 6 mm soft metal alloys

I can get HSS or tungsten-vanadium drills. Not sure about carbide? What material wears the least, what's less likely to break?
 
HSS is probably fine. Even the min. speed of 3K is way too fast for drilling though - even with those small sizes.
 
Mind wonders to what mori is up to and why he is always so curious about drill bits.

Are those moto-tool type speeds?

They'll both break, tungsten-vanadium will wear for a long time with the softer alloys and drill better through the steel (use a coolant if you can). HSS if you just want to chuck them....
crackmeup2.gif


Can you get cobalt alloy bits?
 
HSS will take care of anything you mention. I'n not too familiar with T-V but appears to be for non-ferrous materials. Tungsten-Carbide is really tough stuff but is initially not as sharp as HSS, over its lifespan it will maintain its edge longer then HSS.
 
Originally Posted By: NJC
HSS is probably fine. Even the min. speed of 3K is way too fast for drilling though - even with those small sizes.

Bad info with the drill RPM - that's way faster than I'd spin it but drill charts speak otherwise.
 
Originally Posted By: NJC
HSS is probably fine. Even the min. speed of 3K is way too fast for drilling though - even with those small sizes.


3k rpm is normal idle speed. I can reduce speed further (to zero), for example for cutting threads. The tungsten-vanadium bits, even the 0.5 mm ones, are rated up to 8k rpm for soft metal and up to 3k rpm for hard metal. 5k rpm cause no problem when drilling thin steel.

Runout is >/= 1/100 mm. I break drills less often with the machine compared to using a hand-held, manual drill. The tungsten-vanadium drills seem very flexible, but they cost at least double of the HSS drills.
 
Originally Posted By: Pablo
Mind wonders to what mori is up to and why he is always so curious about drill bits.

Are those moto-tool type speeds?

They'll both break, tungsten-vanadium* (wrong - should be TITANIUM-NITRIDE) will wear for a long time with the softer alloys and drill better through the steel (use a coolant if you can). HSS if you just want to chuck them....
crackmeup2.gif


Can you get cobalt alloy bits?


*Brainfert alert....please substitute TITANIUM-NITRIDE above!!!

I rarely see tungsten-vanadium twist drill bits. Mostly burr types.
 
Originally Posted By: NJC
Originally Posted By: NJC
HSS is probably fine. Even the min. speed of 3K is way too fast for drilling though - even with those small sizes.

Bad info with the drill RPM - that's way faster than I'd spin it but drill charts speak otherwise.


The speeds sound reasonable. I calculate 3600 rpm max for a 2mm hss bit in mild steel. What does your chart say?

If the steel has been hardened, a lot slower.

For aluminum and brass, a lot faster would be OK
 
Originally Posted By: Pablo
I rarely see tungsten-vanadium twist drill bits. Mostly burr types.


The mill maker offers tungsten-vanadium drill bits from 0.5 to 2.1 mm. They also have "hard metal" (they don't specify what material) drill bits from 1 to 2 mm. These are for drilling glass and stone. The cheaper option are HSS drills. In my hand-held, manual drills the HSS drills work best (reasonably well without breaking soon).
 
I don't care for carbide drills in small holes they tent to shatter if they load up. Though if they load up your chip load is wrong.

In this application I would use a cobalt drill with a high helix. 2nd choice would ti coated HSS. Having said that don't underestimate how important a good grind quality is. There are a lot of garbage drills poorly ground available these days. Hint Japanese generally make very good drills.
 
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it don't matter what you use so long as you use it properly. just like in the bedroom.

I have had a lot of experience with drilling things since i am a mechanical person and i like to try and fix things myself.
i have found that in nearly every application, i need to set my drill press to it's lowest speed possible. then i do all the drilling i possibly can while the part is submerged in a water oil mix similar to what cnc users run. i don;t have a pump and nozzle or anything like that. just a good ol oil and water bath does the trick.
if the part is too big to submerge, i splash lube it as best i can while drilling slow and stopping for 30 seconds at a time every minute.

you can get AWESOME cutting speed and the bits will last forever if you keep them cool. heat is the #1 enemy of drill bits. if you smoke a bit then the head is trashed.

i see people all the time with metal bits that wont even cut aluminum because they have been smokes and the heads are disco loured.

do youre drilling just like you do the bedroom kind. low and slow.
 
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I looked at the main catalog and the options for industrial/dental quality are:

- tungsten micro drills, 6° cutting angle
- tungsten carbide milling drills (speardrill)
- diamond twist drills
- HSS twist drills
- tungsten-vanadium with high concentricity for non-ferrous metals
 
Originally Posted By: moribundman

- diamond twist drills

I'd be inclined to stay away from diamond - they are WAY more brittle than carbide. I have broken many of them by simply underestimating their brittle structure. Plus the diamond coating makes them "dull."

My earlier reservation with high drilling speeds is heat and friction instead of chips. Brass is oddball material; copper is gooey; steel is good and alum is the easiest. As others have mentioned, use a light oil (cold-pressed olive oil would do in a pinch) to ensure the flutes don't get packed.

The smaller drills are going to be difficult to not break. Go with the shortest flute length possible and chuck as far in as possible.
 
The diamond-dusted drill bits are for widening existing holes in precious stones, dental ceramics etc. They are not for drilling holes.

The shaft of drills between 0.5 and 2.1 mm is 2.35 mm. I use a very precise three-slit collet for those small drills. I have those also collets in other sizes (1 to 3.2 mm). For larger dill sizes I use an adjustable three-jaw chuck that is little bit less precise but more convenient if I have to change drills frequently. All available drills by the manufacturer are dedicated to their rotary tools.

I'm simply trying to find alternative drill bits. The tungsten-vanadium drills that I'm using are relatively cheap at about $6 for a set of three. The HSS ones are about 75 cents each. The Ti-coated HSS ones I hadn't seen until today and I don't yet know how much those cost. I guess I'll try them.

In the picture you can see an 0.8 mm tungsten-vanadium bit with a 2.3 mm shaft. The fluted area gets shorter with decreasing drill size.

drillandchuck.jpg
 
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